President Obama had a dual mission when he addressed Congress and the country Thursday night: to present a plan to stimulate the economy and, as pressingly, to seize the initiative in a political battle that will be at the heart of the 2012 election.

Reflecting his objectives, the president spoke with a renewed sense of urgency — and with more pointed rhetoric than he often projects from such a weighty podium. He outlined a roughly $450 billion package and called on Congress to pass it right away. But he also used his speech to frame the coming debate over the economy in ways that he hoped would pin the blame on Republicans if they failed to go along.

The address Thursday was the opening round of an administration offensive that will take the president outside Washington to make his case to the American people while Congress deliberates. He was explicit in his warning to the Republicans. “This plan is the right thing to do right now,” he said. “You should pass it. And I intend to take that message to every corner of the country.”

Obama spoke at a low point in his presidency. His standing has been weakened by public dissatisfaction over the effects of high and persistent unemployment. But just as worrisome for the White House are questions about whether he is a leader with the strength and skills to make Washington work — one of the aftereffects of the just-concluded fight over raising the debt ceiling.

Obama spoke directly to the political mood in Washington. “I know there’s been a lot of skepticism about whether the politics of the moment will allow us to pass this jobs plan — or any jobs plan,” he said. “Already, we’re seeing the same old press releases and tweets flying back and forth. Already, the media has proclaimed that it’s impossible to bridge our differences.”

He noted that many in both parties believed that their differences can be resolved only by the next election.

“The next election is 14 months away. And the people who sent us here — the people who hired us to work for them — they don’t have the luxury of waiting 14 months,” Obama said. “Some of them are living week to week, paycheck to paycheck, even day to day. They need help, and they need it now.”

But even as he urged action now before politics consumes the capital, both sides knew that this speech was also a political call to arms.

Obama walked a fine line Thursday. His strong rhetoric and explicit challenge to Republicans, as well as the size and specifics of the package, were designed to appeal to his restive base. His call for the two parties to set aside politics long enough to enact some job-creating measures was aimed at swing voters disgusted by the debt-ceiling spectacle and the sense that Washington is badly broken.

Obama prodded Republicans to approve measures that he said many of them have supported in the past. He salted his package with proposals that he said would create hundreds of thousands of jobs and that White House officials hoped would strike Americans as sensible and appealing.

The measures included a big payroll tax cut for workers and small businesses; aid to states to hire back some of the teachers laid off in the past few years; major investment in infrastructure improvements to rebuild schools and roads as well as other projects.

Obama said all of this could be paid for if the congressional supercommittee that is beginning work raises its deficit-reduction target enough to cover the costs. He also promised to issue his own blueprint for additional deficit reduction.

House Speaker John A. Boehner (R-Ohio) issued a temperate statement in response, saying it was “my hope that we can work together” to aid the economy. But other Republicans weren’t buying, at least not yet.

Sen. Rob Portman (R-Ohio), a member of the supercommittee, chastised the president for “doubling down on his failed” policies and for spending too much time “assigning blame.”

The campaign of former Massachusetts governor Mitt Romney put up a video on its site that included footage of the president in the House chamber and the message that he is 960 days late in issuing a jobs plan. But Romney offered no immediate direct critique.

White House officials hold out some hope that at least some of the measures Obama presented will eventually be passed and implemented, with the payroll tax cut the most likely. But they are also determined not to emerge from this battle with congressional Republicans as scarred and damaged as they were from the debt-ceiling fight.

Obama’s team believes it paid a price not only for raising expectations about the possibility of a grand bargain to reduce the deficit, but also by the messiness of the process — which led to something far short of that. In the battle over job-creation measures, the team intends to avoid a protracted series of negotiations with Republicans behind closed doors, as occurred over the debt ceiling.

“We’re not going to sit in the Cabinet room for weeks at a time,” said a senior White House official, who spoke on the condition of anonymity to discuss the strategy candidly. “We’re just not going to do that.”

That means taking the battle to the public. “People recognize the obstacles here and where they’re coming from,” said David Axelrod, a former White House senior adviser who is chief strategist for Obama’s reelection campaign. “We don’t go up there [to Congress] with the anticipation that nothing will pass and nothing will work. But Harry Truman once said if you can’t make them see the light, make them feel the heat. And that’s what the president is going to do.”

Obama has been in this situation before, but perhaps never in such difficulty as today. More than anything, the president needs the economy to show improvement as quickly as possible. Failing that, he signaled Thursday that he is ready to carry the argument to the American people that Republicans have stood in the way of progress. The future of his presidency will hinge on the outcome of those two tests.

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